This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of this study is to investigate the effects of morbid obesity and weight loss on human reproductive function in patients undergoing gastric bypass surgery. Hypotheses: 1) Morbid obesity leads to reproductive abnormalities in men and women;2) Bariatric surgery alters GI hormone expression producing immediate changes in the hypothalamic-pituitary-gonadal axis.;3) Fat mass reduction causes changes in adipokine levels leading to improved reproductive function. The primary outcome measurement for men is monthly testosterone AUC and for women pregnanediol 3-glucuronide AUC.